In order to determine the concentrations of components such as glucose, and urea nitrogen in blood, heretofore a simple analysis method has been employed in which a coloration test sheet is used. More specifically, in the prior art method, the degree of coloration (i.e., dye formation) of a coloration test sheet is often visually compared with a sample of coloration of a component to be measured which was obtained using the same component a predetermined concentration and the concentration of the component is determined as a result of the comparison. However, that simple analysis method does not have a satisfactory accuracy because the degree of coloration of the coloration test sheet must be determined visually by the operator.
In order to overcome this difficulty, a variety of methods have been proposed in the art in which a reflection type densitometer is used to improve the accuracy of determination of desired parameters of components to be measured.
The dye formed in the coloration test sheet is unstable, because it changes with time, and sometimes fading occurs. Accordingly, for simultaneously processing a number of different samples of materials using coloration test sheets, errors unavoidably occur.
In order to eliminate this drawback, a method of automatically analyzing a component to be measured with an optical device and a device for practicing such a method have been proposed in the art. In accordance with this method and device, a predetermined amount of sample solution to be analyzed is placed on a multi-layer type chemical analysis slide, which was produced by shaping a multi-layer type chemical analysis material (film) into the form of a slide, and containing at least a spreading layer and a reagent layer. The multi-layer type chemical analysis slide is conveyed by a conveying device such as a conveying belt to a controlled-temperature heating unit where it is held at a constant temperature for a predetermined period of time. Thereafter, the slide is irradiated by a measuring irradiation light beam of a wavelength which has been preselected in accordance with the component to be measured and the reagent contained in the reagent layer to measure the reflection factor thereof from which the concentration of the component to be measured can be determined.
However, the automatic chemical analyzer as described above is disadvantageous in that it is considerably bulky because the heating unit must be provided separately from the conveying device making it impossible to miniaturize the analyzer. Moreover, the construction thereof is considerably intricate.